1. Field of the Invention
The present invention relates to a communication support system, a communication support method, a communication support program, and a communication terminal for supporting the establishment of connection between communication terminals including a mobile communication terminal in a computer network used by a mobile communication terminal that performs wireless transmission.
2. Description of Related Art
Recently, for example, as in an IP telephone via a wireless local area network (LAN), a mobile communication terminal that provides a telephone function via wireless network has become widespread. The mobile communication terminal that provides a telephone function via wireless network enables a telephone function with a terminal on a partner side by performing wireless transmission with a relay apparatus (e.g., an access point of a wireless LAN, etc.). In such a wireless data transmission system, a plurality of mobile communication terminals exist in a coverage area of a relay apparatus, whereby a plurality of mobile communication terminals perform wireless transmission with a relay apparatus simultaneously. In this case, a plurality of mobile communication terminals share a transmission bandwidth available in the relay apparatus, and perform wireless transmission respectively. Therefore, in the case where the number of mobile communication terminals that provide telephone functions simultaneously via one relay apparatus increases, the transmission bandwidth becomes insufficient. Consequently, at a mobile communication terminal, delays in audio transmission from a terminal on a partner side is increased, and a noise such as a sound break occurs. This problem may occur in the case of streaming data such as music or a moving picture by streaming, as well as in the case of providing a telephone function.
In order to prevent the shortage of a transmission bandwidth in a relay apparatus, for example, a method has been adopted for rejecting the establishment of a telephone connection via the relay apparatus when the amount of a transmission bandwidth unoccupied by mobile communication terminals in the relay apparatus is not sufficient. Furthermore, in the case where a mobile communication terminal transmits a request for establishing a telephone connection, and the transmission bandwidth unoccupied in the relay apparatus is small, the following method is adopted: the mobile communication terminal is notified of a relay apparatus in which an enough transmission bandwidth for other telephone connections remains sufficiently (for example, see JP 2005-33707 A).
However, the above-mentioned conventional example is effective only when the transmission bandwidth in a relay apparatus of a mobile communication terminal on a calling side is insufficient. In the case where the transmission bandwidth in a relay apparatus of a mobile communication terminal on a receiving side is insufficient, a telephone connection cannot be established. Furthermore, in the above-mentioned conventional example, the following method is adopted: communication is started by moving to a coverage area of the relay apparatus in which an available transmission bandwidth remains sufficiently, followed by retransmitting. However, a mobile communication terminal of a partner, with which the above-mentioned mobile communication terminal desires to provide a telephone function at a time of reconnecting, may have moved outside of the coverage area. In order to establish a telephone connection, it is necessary to set up conditions for starting the communication at both the mobile communication terminals on a transmitting side and a receiving side. For this purpose, it is desired that requested information on the establishing of a telephone connection be delivered to both the mobile communication terminals.